This invention relates to the field of electronic control circuits for domestic washing appliances such as dishwashers. More specifically, it relates to control circuits for a dishwashing appliance of the type disclosed in the above-identified related applications in which a microprocessor performs the control functions conventionally performed by a electromechanical sequencer or controller.
In domestic washing appliances such as dishwashers and clothes washing machines, it is desirable to enable the user to manually return the controller to the beginning of the operating cycle at any time in the cycle. In the case of the electromechanical controller, the user merely manually advances the cycle control knob to the start position. However, in the case of a microprocessor based control system, there typically is no control knob to advance. In addition, it is possible that abnormal transient electrical signals applied to the microprocessor may "confuse" the microprocessor during normal microprocessor operation. This condition typically may be corrected merely by resetting the microprocessor. It is desirable therefore to provide a manually operable means by which the operator may reset the microprocessor, thereby interrupting or canceling appliance operation and returning the control program to its starting point. In addition, it is desirable when returning to the starting point in response to a manual reset to remove any water which may have been in the appliance at the time operation was interrupted, as would be the case if a wash or rinse cycle is in progress when the interruption occurs.
It is therefore an object of the present invention to provide a control circuit for a microprocessor controlled washing appliance which enables the user to manually reset the microprocessor.
It is a further object of the present invention to provide a control circuit for a microprocessor controlled washing appliance which enables the user to manually reset the microprocessor and initiate a drain cycle to remove and water from the appliance in response to the manual reset.
It is a further object of the present invention to provide a control circuit for a microprocessor controlled washing appliance which generates a microprocessor reset signal and an initiating signal in response to a manual input, such that the initiating signal is delayed in time relative to the reset signal by a predetermined period.
It is a further object of the present invention to provide a control circuit which performs the above-described functions in time synchronization with the external interrupt timing of the microprocessor.